LONDON, June 22 (Reuters) - European shares were in store for another weak session on Thursday, pegged back by the slide in commodities-related sectors on the back of depressed oil prices.

The pan-European STOXX 600 index was down 0.4 percent, on track for its third day of straight losses, while the blue chips dropped 0.6 percent.

The price of oil fell further as worries persisted over global oversupply, with Europe's energy sector down 1.5 percent, close to 7-month lows, and mining stocks also retreated 0.7 percent.

"What didn't help were those conflicting comments from OPEC ... and Iran. They need to be singing from the same hymn sheet if we are to believe that there's positivity to be taken from these cuts while the U.S. continues to produce more and the rig-count goes up," Mike van Dulken, head of research at Accendo Markets, said.

"As we saw yesterday, even a drawdown in stockpiles offered absolutely no help because it just added to the murky outlook."

Health care was the top-gaining sector, however, up 0.7 percent with Switzerland's Novartis in the driving seat as its shares advanced nearly 3 percent, following a positive study result for its canakinumab medicine, which cuts risks for heart attack survivors.

"Expectations around this catalyst have been low and as a result we have previously highlighted success could drive 3% to 5% upside to mid-term EPS and valuations," analysts at Jefferies said in note.

Elsewhere, Imagination Tech, once a high flyer as a supplier of graphics technology to Apple <AAPL.O, soared more than 20 percent after it put itself up for sale.

In April, Apple said that it would no longer use Imagination's graphics technology in the iPhone, wiping out more than 60 percent of the British firm's market value.

Broker action also lifted shares in industrial machinery firms Rotork and Alfa Laval, which both rose more than 3 percent following double upgrades from Morgan Stanley to "overweight".

The broker said that it was positive on forecasts for Alfa Laval's divisions, and saw growth potential for Rotork's products.

Morgan Stanley was more pessimistic around the oil sector, however, with analysts saying in a note that they expected concerns around a 2018 oil supply glut to weigh.

This put pressure on shares in Subsea 7, Amec Foster Wheeler, TGS NOPEC Geophysical Company and Tullow Oil, which were all down between 2.6 to 4.8 percent at the bottom of the STOXX. (Reporting by Kit Rees, Editing by Vikram Subhedar)